Transfer control system



April 1949- w. R. TALIAFERRO 2,468,135

TRANSFER CONTROL SYSTEM Filed April 5, 1945 Main 15' A9 fl/ZermzfeSource Source WITNESSES: INVENTQR Q12)- MW BY ATTO EY Patented Apr. 26,1949 TRANSFER CONTROL SYSTEM William R.

Taliaferro, Edgewood, Pa., assignor to Westinghouse ElectricCorporation, East Pittsburgh, Pa, a corporation of PennsylvaniaApplication April 3, 1945, Serial No. 586,386

'7 Claims. 1

My invention relates generally to control systems and has reference, inparticular, to circuit breaker control systems.

Generally stated, it is an object of my invention to provide a circuitbreaker control system that is simple and inexpensive to manufacture andis reliable in operation.

More specifically, it is an object of my invention to provide ananti-pump circuit breaker control system for effecting transfer of a busfrom one power source to another.

It is'also an important object of invention to provide'a control systemfor looking out a circuit breaker against r-eclosure after theoccurrence of afault condition.

"Another object of my invention is to provide a load bustransfer systemwherein the bus is normally connected to a main source and isautomatically connected to an alternate source as soon as thevoltage ofthe main source falls below a predetermined. value.

Yet another "object of my invention is to provide for preventingreclosure of one of a pair of bus transfer circuit breakers supplyingelectrical energy to'a load circuit when a fault condition; which causesthe opening of the circuit breaker, results in an appreciable reductionin the circuit voltage.

Still another object of my invention is to provide for reenergizing thecut-off relay of a circui't breaker which is opened a fault conditionthatresults in the circuit voltage being appreciably reduced, in orderto prevent reclosure of thecincuitbreaker by its closing relay upon thereturn of the voltage to normal.

-Yct another object of m invention is to provide an automaticbustransfer system having overload protection for the alternate powersource circuit breaker.

wIt'is also an object of my invention to provide for automaticallydisconnecting a bus from a main orncrmal-power source and connecting ittoan emergency or alternate power source upon the occurrence of a fault,and for tripping and locking out the emergency circuit breaker, shouldthe fault still bepresent.

Other objects will. in part. be obvious and will, in part, be explainedhereinafter.

-In practicin my invention in one form thereof, the load is normallyconnected to a load bus which is energized from a main power sourcethrougha main circuit breaker. Overload protection is provided by afeeder circuit-breaker at the source. An auxiliary cr'alternate circuitbreaker having overcurrent trip is provided so that the load bus may beconnected to an alternate -or emergency power source as soon as thevoltage of the main power source fails for any reason, provided thevoltage of the alternate power source is normal. Induction type voltagerelays, having a delayed closing time, are-used to open the main circuitbreaker and effect thedesired transfer operation. The voltage relayassociated with the auxiliary circuit breaker provides an energizingcircuit for the circuit breaker cut-off relay whenever voltage isrestored after the occurrence of a fault which appreciably: reducesthe-circuit voltage and causes the auxiliary circuit breaker to open,502.5 to prevent reclosure of the auxiliary circuit breaker. vThevoltage relay of the main circuit breaker effects tripping of theauxiliary circui-t breaker whenever the voltage of the main power sourceisrestored, thus making this source the preferred one. For a furtherunderstanding of the nature and scope of my invention, reference may bemade to the following detailed descriptionwhich may be studied inconnection with the accompanying drawing, in which the single figure isa diagrammatic view of a bus transfer system embodying the invention inone of its forms. 7

Referring to the single figure of the drawing, the reference numeral inmay denote generally a bus transfersystem wherein a load ll connected toa load bus I2 is normally disposed to be connected by means of a maincircuit breaker M to a main or preferred power source l5,'as shown, andwhich may comprise a main feeder bus having suitable overload protectionof any well known type. An auxiliary circuit breaker l1 may be providedfor connecting theload bus I 2 to an alternate or emergency power sourceI9, as shown, and which may comprise, for example. a Diesel enginedriven generator. For the purpose of simpl fication, the system is shownin its normal operating condition with the main circuit breaker [4closed and the load II connected to receive power from the normalpcwersource l5. The emergency power source I9 is shown as havingsubstantially normal voltage.

The main circuit breaker l4 may be of any suitable type having maincontact members Ma, l ib, M0 for connecting the conductorsof the loadbus !2 to the normal power source. Thiscircuit breaker may be providedwith a closing solenoid ill) for operating an armature 2! connected tothe operating lever 22 by a closing latch mechanism 23. It also may beprovided with a mechanical trip mechanism comprising a plunger 25 forrotating the operating lever 22 about a pivot point in acounterclockwise direction to release the holding latch 27. The breakermay be'tripped electricall by trip means 28 comprising an-operatingwinding 29 for actuating "an armature 35 to .pivot the operating lever22 in a counterclockwise direction for likewise releasing the latch 21.

Control of the main breaker 14 may be efiected in the usual manner bymeans of a closing relay 32 provided with an operating winding 33' foroperating the relay to connect the solenoid winding 20 to the source. Acut-off relay 35 having an operating winding 35, disposed to beenergized when the breaker closes, provides for deenergizing the closingrelay 32.

The auxiliary or circuit breaker I1, which is shown in the openposition, may be provided with main contact members Ila, llb, Ilc forconnecting the load bus l2 to the emergency or alternate power sourceI9. This circuit breaker may have an operating winding 4!! for actuatingan armature 4| connected to an operating lever 52 by a closing latchmechanism 43. The breaker may be tripped mechanically by means of aplunger 45 disposed to actuate the operating lever $2 in a clockwisedirection about a pivot to release a holding latch 41. Electricaltripping may be effected by trip means 48 comprising a trip winding 49for actuating armature 53 to pivot the operating lever 42 for releasingthe latch 41.

In order to protect the alternate source l9 against overload conditions,the breaker ll may be provided with overcurrent trip means 5! comprisinoperating. windings Ela, 51b and 510 disposed to be connected in seriescircuit relation with the conductors from the alternate source IQ foractuating the operating lever 42 to trip the breaker.

Control of the auxiliary breaker I! may be effected in the usual mannerby means of a closing relay 52 having an operating winding 53 foroperating the relay to connect the operating winding 40 of the breakerI! to the alternate source. A cut-off relay 55 having an operatingwinding 56 may be provided for deenergizing the operating winding 53 ofthe closing relay 52 when the breaker ll closes.

In order to make the main source 15 the preferred source and to providefor transferring from one source to the other only when the voltage ofthe source to which the transfer is to be made is substantially normal,means, such as the voltage relays E and 6!, may be provided inconnection with the normal and alternate sources l and I9, respectively.The voltage relays 5!! and 6! may be of the induction type havingrotating discs 52 and 63, respectively, for operating contacts 66a andfiiib in accordance with the voltages of their respective sources. Theserelays because of their operating characteristics provide an inherenttime delay and prevent tripping on momentary voltage dips, since apredetermined time interval is required for operation of their contactsafter the relays are energized or deenergized.

Auxiliary relays E5 and 56 having operating windings '61 and 58,respectively, may be provided for operation under the control of theirrespective voltage relays es and 6!. These auxiliary relays may bedisposed to remain in the energized position until the voltages of theirrespective sources drop below a predetermined value, for example, about50%.

By using the auxiliary relay 55 to complete a tripping circuit for thetrip means 48 of the auxiliary breaker II, this breaker may be opened toprovide for transfer of the load bus l2 to the normal power source I 5 apredetermined time after the voltage of this source returns tosubstantially normal value. By using back contact members of theauxiliary relay 55 and front contact members of the auxiliary relay 6%for energizin the trip means 28 of the main breaker, the tripping ofthis breaker is efiected only when the voltage of the main or normalpower source is reduced below the predetermined value, and the voltageof the alternate power source is of substantially normal value.

Whenever the auxiliary breaker IT is tripped by its overcurrent tripmeans 5! without the voltage of the alternate power source droppingbelow the predetermined value, reclosure of the breaker I1 is preventedby reason of the cut-01f relay 55 remaining energized, so as to preventoperation of the closing relay 52.

In order to prevent reclosure of the auxiliary breaker I'l whenever itis opened in response to a fault condition which reduces the voltage ofthe alternate power source to such a value that the cut-off relay 55 isdeenergized, means may be provided for insuring reenergization of thecut-oil relay 55 immediately upon the return of the voltage of thealternate power source to normal value. For example, the energizingcircuit for the operating winding 56 of the cut-off relay 55 may becompleted through normally closed contact members 66d of the auxiliaryrelay 65. Since the auxiliary relay 66 will likewise be deenergized whenthe voltage of the alternate power source I9 drops below thepredetermined value, and it cannot be reenergized for a predeterminedtime until a voltage relay 6| again operates, a positive energizingcircuit is provided for the cut-off relay 55, so as to effectdeenergization of the closing relay 52 as soon as the voltage of thealternate power source is restored. Reclosure of the auxiliary breakerI! is thus prevented. After the breaker ll has been locked out due to afault condition which reduces the voltage of the alternate power sourceI9 below the predetermined value, the circuit control may be reset byoperating a push button switch 10 which disconnects the cut-01f relay 55from a source and restores it to the deenergized position.

With the transfer system in the normal operating condition, as shown,the main circuit breaker I4 is closed connecting the load H and the loadbus I2 to the normal power source I5 through contacts Ma, Mb and 140.Should a fault or other condition occur which opens the feeder circuitbreaker at the source or otherwise reduces the voltage of the normalpower source 55 below the predetermined value, the auxiliary relay E5and the cut-off relay 35 return to their deenergized positions. If thevoltage of the alternate power source i9 is substantially normal, theauxiliary relay will have been operated to the energized position by itsvoltage relay 6! wherein it is retained by an energizing circuit throughcontact members 66?). The voltage relay 6! is deenergized by the openingof contact members 66a. Since the main breaker I4 is in the closedposition, an energizing circuit is established for the trip winding 29of the main breaker I 4, extending from the alternate power source l9through conductor 12, the reset push button switch 10, conductor 13,contact members 660 of the auxiliary relay 66, contact members 650 ofthe auxiliary relay 65, conductor 15, contact members 14d of the breakerl4, operating winding 29 and conductor 15 back to the alternate powersource l9 through conductor 11. The main breaker in is accordinglyopened.

As soon as the main breaker 14 opens, an

'5 energizingizcircuitriss established for the closing relay 252: of:the". auxiliary circuit breaker H extending j 'fromw thea; alternatepower source l9 through: conductor .12," reset-push button switch 10,:conductor 18,: conductor '59, back contact members-"55bofxthe'rcutoifrelay 55, operating winding 53;; conductor 88, backcontact members I 4e1of .the breaker. M;- ;conductor 16 and'conduc-.tor'l'h back to-sthe alternate power source iii. The closing relay 52:operates to connect the operating winding'4fl;,of"theiauxiliary breakerH to the alternateapowersource' 19. through contact members 152a.aAsxsoon .asm'omentary contact members ITfiDf the breaker .iI-close, theoperating windin 5.6of-the cut-off relay 55 is energized, sincercontactimembers Me of 'theniain breaker -14 aremow closedpand thecut-offxrelay operates to deenergize- :theoperating-winding 53 of theclosing re'layi52. 'A" holding tcircuit" is providedfor-theoperatingxwinding 56. of the cut-ofi relay 55 through contactmembers 55a.

w Should the voltage of the normal power source :l5 be restored;theavoltage relay it} operates after a: predetermined time delay toclose its contact members: 60a. The-operating winding 51' of theauxiliary relay-55 is thus energized, and the aux iliary;relayi65returns to the energized position, deenergizing' the voltage relay 6G byopening contact-members 65axand locking itself in throughconta'cttmem-bers :55b. :At the same time an energizing circuit isestablished for the tripmeans 4810f the auxiliary breaker ll extendingfrom the normal"poivers'source 15 through conductor 52, conductor 83';operating winding d9, contact members l-Icl, contacbmembers 65d to thenormal power source throughconductor'll l. The auxiliarybreaker 11opens. An energizing circuit is thereby provided for the operatingwinding 33 of the closingerelayt32, extending from the normal source I5through conductorSZ, conductor 83, contactmembers'l'le, operating windin33, contact members 3512 to the :normal' power source througlrconductor-B4. The closing relay 32 operates to.connect-:theoperating winding 26 ofa main ebreaker M to: the normal power source through contact members32a to effect closure of the main breaker. Upon closure of the mainbreaker. M;the operating'winding36 of the cutoff relay'35 isenergizedthrough contact members-14f. Thecut-off relay thereby operatesto deenergize @the operating winding'33 by opening its contact members.351), A holding circuit is providedthrough contact members 35a.

Shouldthe auxiliary breaker ll be tripped by the overcurrent trip" means5% while it is in the closed position and the'main breaker M remainsopen, reclosure of the-auxiliary breaker ll is prevented if the voltageof the alternate source I9.does not drop below the predetermined value.since the cut-off relay55 remains in the energized position, thus.interruptingv theenergizing circuit for the operating-winding 53of thclosing relay 52v at its contact members Should the auxiliary breaker II be tripped by the overcurrent trip means 5| under fault conditionswhich. reducethevoltage-ofvthe: alternate source it below thepredetermined value, both the cut-elf relay 55 and the auxiliary relay66 will be deenergized. Uponrestoration ofthe voltage of the alternatesource l9, which will normally. occur when the auxiliary breaker l1disconnects the alternate power source'from the load bus, the closingrelay 52 will-tend to operate since a circuit is establishedtthereforthrough contact. members 55?) of thercut' omrelay 55. Howevergatthe sametime,

an energizing. circuit is established'for the-toperating winding 56 ofthe'cuteoff relay through back contact members 66d'of the'auxiliaryrelay 66. This relay was also deenergized uponfailure of thevoltage of the alternate ,sourcel9, and cannot'be reenergized for apredetermined time after the-restoration of voltageysincethe voltagerelaytl \is of theinductiontype and.requires a predetermined time afterthe application f'voltage before closingits'contactmembers50b.=Accordingly, the cut-off relay '55 operatesat-about the same time or before the closingrelay-Stand interrupts theenergizing circuit for the operating winding 53 of the closing relay 52atcontact members 55 b. Therefore, theauxiliary-brea-ker ll cannotreclose, and the cut-off relay I55'.I8- mains in the energized positionlocking the breaker I! out.

Restoration of the system maybe effectedby opening the reset push-buttonswitch 10 .to deenergize the operatin winding '56 of the cut-off relay55. If the voltage of the alternate source l9 has been restored for thepredetermined time interval, the voltage relay 55 will have'operated toestablish an energizing circuit for the operating winding 68 of theauxiliary relay 56. Ac-- cordingly, as soon as the cut-off relay55:1eturns to its deenergized position, an energizing circuit isestablished for the operating winding 53 of the closing relay 52, andthe auxiliary breaker '11 may be reclosed.

From the above 'descriptionand the accompanying drawingit will beapparent that Ihave provided in a simple and efiective-manner forpreventing pumping of a'circuit' breaker "in a bus transfer systemWhichis provided with overcurrent trip rotection. Transfer of the'loadbus from the main power source to' the alternate power source and viceversa is entirely-"autoa matic, and lock-out is eifected upon theoccurrence of fault conditions underwhichdt is undesirable to attempt toeffect-recl'o'sure of the circuit breakers. The system' 'ofmy'inventionis simpleand effective and requires a minimum amount ofapparatus.

Since certain changes may be made 'in the above describedcontruction,"and'difierent embodiments of the invention maybe madewithout departing from the spirit or'scopethereof, it is intended'that'all the matter contained in the above description and shown in the"accompanying'drawing shall be considered as illustrative and not in alimiting'sense.

I claim as my invention:

1. A control system foracircuit breaker connecting a load to a source ofelectrical energy comprising a closing'relay for operating the circuitbreaker, a cut-off'relay operable to render the closing relayinoperative, control means'responsive to the voltage of the source fortripping the circuit breaker when the voltage of the source drops to apredetermined value, additional control 'means responsive topredetermined current conditions for tripping the circuit breaker, andcircuit means including means responsive to a predetermined "reductionin the voltage of the source to provide for energization of the cut-offrelay as soonas the'voltage of the source is restored for preventingoperation of the closing means to'reclose the auxiliary 'circuit breakerafter it opens.

2. A transfer system for a bus'having aipair of circuit breakers forenergizing the bus from main 'and alternate power sources 'compri'sing,controls means including .a closing relay 'and .134

cut-oil relay operable to energize the closing relay for closing themain circuit breaker when the voltage of the main source is above apredetermined value and the auxiliary circuit break er is open, closingmeans including a closing relay and a cut-off relay operable todeenergiae the closing relay responsive to the voltage of the alternatesource when the main circuit breaker is open for closing the auxiliarycircuit breaker, control means responsive to voltage conditions the mainsource for tripping the c'rcuit breaker when the voltage of the mainsource drops below a predetermined value and ti ,lng the auxiliarycircuit breaker when the voltage of the main source is restored, wherebythe main circuit breaker closing means recloses the main circuitbreaker, and circuit means associated with each of the circuit breakersconnected to provide an operating circuit for its associated cutoifrelay as soon as voltage is restored to its associated source forpreventing any reclcsure of its associated circuit breaker.

3. The combination in a transfer for a bus having a main circuit breakerfor connecting it to a main source and an auxiliary circuit breaker forconnecting it to an alternate source. of circuit means including closingfor normally elfecting closure of each of the circuit breakers inresponse to predetermined voltage conditions of its associated sourcewhen the other circuit breaker opens, cut-oil means openable to effectdeenergization of the closing means, control means for each of thecircuit breakers effecting opening of said circuit breakers, means fortripping the auxiliary circuit brea in response to a fault condition andcircuit means responsive to a reduction of the voltage of the alternatesource providing an operating circuit for the cut-off means forpreventing operation of the closing means to reclose the auxiliarycircuit breaker when the voltage of the alternate source is restored.

4. A transfer system for a load bus having main and auxiliary powersources of electrical energy comprising, a main circuit breaker fornormally connecting the load bus to the main source, an auxiliarycircuit breaker for connecting the load bus to the auxiliary source,closing means responsive to voltage conditions of the sources forproviding an operating circuit for the auxiliary circuit breaker whenthe main circuit breaker is open, a cut-off relay responsive to apredetermined voltage of the auxiliary source for deenergizing theclosing means when the auxiliary circuit breaker closes, means foropening the main circuit breaker When the voltage of the main sourcereaches a predetermined minimum value and tripping the auxiliary circuitbreaker when it reaches a predetermined normal value, and control meansresponsive to a reduction in voltage of the auxiliary source forpreventing reclosure of the auxiliary circuit breaker by providing anoperating circuit for the cut-ofi relay before the auxiliary circuitbreaker closes.

5. For use with a load circuit having main and auxiliary power sources,a main circuit breaker for normally connecting the load circuit to themain source, an auxiliary circuit breaker provided with overcurrent tripmeans for connecting the load circuit to the auxiliary source, controlmeans responsive to the voltages of each of the sources for normallyeffecting closure of their respective circuit breakers when the othercircuit breaker is open, circuit means including relay means responsiveto the voltage of the main source and relay means responsive to thevoltage of the auxiliary source for tripping the auxiliary circuitbreaker when the voltage of the main source is substantially normal andfor tripping the circuit breaker whenever the voltage of the main sourcedrops to a predetermined value below normal, provided the voltage of theauxiliary source is substantially normal, and circuit means includingcontact means responsive to a reduction in the voltage of the auxiliarysource when the load circuit is connected thereto for looking out theclosing means as soon as the auxiliary circuit breaker opens to preventreclcsure of the auxiliary circuit breaker.

6.1-1 transfer system for a pair of circuit breakers for connecting aload bus to main or alternate power sources comprising, closing meansfor each of the circuit breakers, circuit means for operating theclosing means of each circuit breaker when the other circuit breaker isopen, additional circuit means connected for tripping one of the circuitbreakers only when the voltage of the other source is normal, meansresponsive to predetermined current conditions for tripping the onecircuit breaker, and means responsive to a predetermined reduction inthe voltage of the source associated with said one circuit breakerelfective to prevent reclosure of said circuit breaker when the voltagethereof is restored.

'7. A transfer system for energizing a load bus from one or the other ofa main power source and emergency power source comprising, a n circuitbreaker for normally connecting the bus to the main source, an auxiliarycircuit breaker connecting the bus to the emergency source when the maincircuit breaker is open, means including a closing relay for closingeach of the circuit breakers when the other circuit breaker is open. aout-05f relay for each circuit breaker disposed to be energized when thesaid circuit breake: closes to deenergize the closing relay, said cu offrelay being provided with a holding circuit so long as the voltage ofits associated source remains substantially normal, shunt trip means foreach of the circuit breakers, means responsive to the voltage of themain source for energizing the shunt trip means of the auxiliary circuitbreaker when it is closed if vclt e of the main source is substantiallyrmal ol prepare for energizing the shunt trip means of the main circuitbreaker When the voltage of the main source drops below a predeterminedvalue for a predetermined time, and means responsive to the voltage ofthe alternate source for cooperating with the means of the main sourceto provide for energizing the shunt means of th main circuit breakerwhen the voltage of the alternate source is substantially normal and toprovide an energiz ng circuit for the cut-oi f relay of the auxiliarycircuit breaker voltage is restored after a fault condition whichreduces the voltage of the auxiliary source to prevent reclosu e of sa dcircu t b e ker.

WILLIAM R. TALIAFERRO.

CE'EEB The following references are of record in the fi e of thispatent:

UNITED STATES PATENTS Number Name Date 2,018,495 Hoifmann Oct. 22, 19352,172,950 Anderson Sept. 12, 1939

